1. Field of the Invention
The present invention relates generally to shock-resistant circuit breakers and, more particularly, to a shock-resistant circuit breaker having an under-voltage release mechanism employing a resilient mount.
2. Description of the Related Art
Numerous types of circuit breakers are known and understood in the relevant art. Among the purposes for which circuit breakers are provided is to interrupt an electrical circuit on command or according to certain criteria. For instance, a given circuit breaker may be configured to interrupt a circuit during one or more specific overcurrent or an under-voltage conditions or other conditions. Circuit breakers typically include a set of moveable electrical contacts that are placed into a compressive abutting relationship with a set of stationary contacts to complete an electrical circuit. If it is desired to interrupt the electrical circuit, the moveable contacts are moved by a tripping mechanism away from the stationary contacts to break the electrical connection between the moveable and stationary contacts and to interrupt the electrical circuit. Numerous types of tripping mechanisms exist and are often tailored to meet specific needs of particular applications.
In multiple-pole circuit breakers, such tripping may occur by rotation of a trip bar to rapidly and simultaneously separate the moveable contacts from the stationary contacts of all of the poles to interrupt the electrical circuit. In such configurations, it is often desirable to additionally provide one or more trip buttons to enable rotation of the trip bar to operate the circuit breaker interruption mechanism during certain conditions. Such a trip button may be depressed manually or by a plunger of a trip mechanism, or may be operated by other electrical apparatus as needed for the specific application.
One such type of trip mechanism that may be used to engage a trip button of a circuit breaker is an under-voltage release mechanism. Such under-voltage release mechanisms employ a magnetic tripping device that includes a coil, a magnetically permeable core, and a magnetically permeable and movable plunger, as is generally known and understood in the relevant art. When the circuit breaker is in operation and the movable contacts are engaged with the stationary contacts, the coil is energized, whereby the plunger is magnetically biased against a spring. In such conditions, the magnetic interaction between the core, the plunger, and the magnetic field generated by the coil magnetically biases the plunger to overcome the spring and to retain the plunger in a retracted position and to keep the plunger away from the trip button. When the circuit voltage drops below a given preset level, however, the magnetic field generated by the coil becomes insufficient to overcome the force of the spring, with the spring then biasing the plunger into an extended position. The plunger in the extended position operatively engages the trip button to initiate rotation of the trip bar and interrupt the electrical circuit.
While such under-voltage release mechanisms have been effective for many of their intended purposes, such under-voltage release mechanisms are not without limitation. For instance, circuit breakers employing such under-voltage release mechanisms are subject to inadvertent and inappropriate tripping during shock loading of the circuit breaker. Such inappropriate tripping is to be particularly avoided in critical applications in which the loss of power would create an unsafe or harmful situation. It is thus desired to provide an under-voltage release mechanism that is resistant to shock loading, yet is capable of engaging the trip button of a circuit breaker under appropriate conditions.